Porous Membrane Solder Particle Manufacturing
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Solution Overview
Problem
Current methods for manufacturing solder particles result in a mixture of large and small particles, leading to incomplete filling of minute holes and poor paste transfer during solder bump formation on small chip-type parts, necessitating a classification step that causes oxidation issues.
Innovation Solution
Forcing liquid metal coarse particles through a porous membrane with a heat-resistant continuous phase liquid under pressure to produce fine particles with a diameter equal to or smaller than the membrane's pore diameter, allowing for controlled particle size and preventing oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional manufacturing methods (atomizing, rotating disk, agitation-dispersion) are used to produce solder particles, then production efficiency is maintained, but the particle size distribution becomes wide with large particles (100 micrometers or larger) mixed with fine particles
Solution Approach 1:
The patent employs a porous plate with controlled pore diameters (5-10 micrometers) as the core component to mechanically filter and size-sort solder particles during the manufacturing process. The porous structure allows fine particles to pass through while retaining larger particles, achieving precise particle size control without sacrificing production efficiency. This directly addresses the contradiction by using the porous material's physical structure to enforce size uniformity while maintaining continuous production capability.
Solution Approach 2:
The invention segments the particle size control process by using multiple porous plates with different pore diameter specifications arranged in sequence. This segmentation approach divides the size control into stages, allowing progressive filtering to achieve uniform particle sizes in the 5-10 micrometer range. The segmentation principle resolves the contradiction by creating distinct size control zones that prevent large particles from contaminating the final product while maintaining efficient throughput.
2Manufacturing precision
If a classification step is added to control particle diameter for neat printing, then printing quality improves, but oxidation of solder particles occurs during handling
Solution Approach 1:
The patent performs particle size classification and control during the primary manufacturing process itself, rather than adding a separate classification step afterward. The porous plate filtering action occurs while the solder is still in molten or semi-molten state within the manufacturing apparatus, creating uniformly sized particles before they are exposed to air and potential oxidation. This preliminary action resolves the contradiction by achieving size control at the source, eliminating the need for subsequent handling steps that would cause oxidation.
Solution Approach 2:
The porous plate acts as an intermediary mechanism that performs size control without requiring the solder particles to be separated, handled, or transferred through additional processing steps. By integrating the sizing function directly into the manufacturing apparatus, the porous plate mediates between the molten solder and the final particle product, achieving precise size control while keeping the process continuous and closed, thus preventing oxidation exposure.
3Quantity of substance
If mixed particle sizes are used in solder paste, then material utilization is efficient, but paste transfer becomes poor and holes in mask are not completely filled
Solution Approach 1:
The patent applies local quality control by ensuring that each particle in the solder paste has a uniform size within the optimal 5-10 micrometer range, rather than accepting a wide distribution. This uniformity ensures that particles of appropriate size can effectively fill the specific dimensions of mask holes and paste transfer gaps. The local quality principle resolves the contradiction by optimizing particle characteristics for the specific application requirement, achieving complete hole filling and reliable paste transfer while maintaining efficient material utilization through the controlled size range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables neat printing and improved solderability on minute portions by ensuring uniform particle size, reducing oxidation and enhancing the reliability of solder bump formation.
Implementation Method 1
Forcing liquid metal coarse particles through a porous membrane with a heat-resistant continuous phase liquid under pressure to produce fine particles with a diameter equal to or smaller than the membrane's pore diameter
Implementation Method 2
Forcing liquid metal coarse particles through a porous membrane with a heat-resistant continuous phase liquid under pressure
Implementation Method 3
a continuous phase of a heat resistant liquid at a temperature of at least the melting point of the low melting point metal
Data Source
AI summary
In a solder paste which is a mixture of a flux and low melting point metal particles, low melting point metal fine particles manufactured by a conventional method or apparatus therefor include particles having widely varying particle diameters. Accordingly, the solder paste could not completely fill the minute holes in a mask for application to minute solder portions by printing, or mask removability was poor. According to the present invention, a mixture of a heat resistant continuous phase liquid and coarse metal particles in molten state is passed through a porous membrane to form the coarse low melting point metal particles into fine particles with a predetermined diameter. An apparatus according to the present invention comprise a porous membrane between a heating and dispersing mechanism and a cooling mechanism, and a pressure vessel connected to the heating and dispersing mechanism for applying a high pressure to the heating and dispersing mechanism.